One of ophthalmic diagnostic apparatuses is a tomography apparatus that utilizes optical interference of so-called optical coherence tomography (OCT) to capture tomographic pictures of ocular fundi. Such a tomography apparatus can irradiate an ocular fundus with low-coherence light of broadband as the measurement light to capture tomographic pictures of the ocular fundus with high sensitivity through interference of the reflected light from the ocular fundus and reference light.
Such a tomography apparatus is capable of three-dimensionally observing the state inside the retinal layers. For example, it is possible to quantitatively diagnose the stage of progression of ophthalmic disorder, such as glaucoma, and the degree of recovery after the treatment through measurement of the layer thickness of a retinal layer, such as a nerve fiber layer, or the change in a layer shape, such as irregularities, on a retinal pigment epithelium layer.
Patent Literature 1 describes a configuration for detecting the boundary of a retinal layer from a tomographic picture captured by a tomography apparatus and extracting exudates as one of lesions from the ocular fundus image.
Patent Literature 2 describes a configuration for identifying an artifact region in the tomographic image of an ocular fundus, detecting the boundary of a retinal layer in a region that is not an artifact region, detecting the boundary of a retinal layer in the artificial region on the basis of luminance values in a different method, and superimposing and displaying lines that represent the detected boundaries.
Patent Literature 3 describes a configuration for detecting layers on the basis of edges lying from a side at which the intensity of signal light obtained from a tomographic image of a subject's eye is low to a side at which the intensity of signal light is high and detecting a layer or layer boundary existing between the layers on the basis of an edge lying from the side at which the intensity of signal light is high to a side at which the intensity of signal light is low.
Patent Literature 4 describes a configuration for preliminarily setting an existence probability model in which the existence probability of brain tissues in the three-dimensional space of an MRI image is modeled, obtaining a tissue distribution model in which both the signal intensity distribution model and the existence probability model are established, and calculating, for each voxel included in the MRI image, a degree of the voxel belonging to white matter tissues and gray white tissues.
Non-Patent Literature 1 describes a configuration for acquiring an edge image of a retinal tomographic picture using a Canny edge detection method, weighting the edge image and a luminance gradient image to calculate them, and searching a shortest route to extract a boundary line of the retinal layer. Non-Patent Literature 1 also describes a configuration for first extracting two boundary lines when extracting boundary lines of a plurality of retinal layers, and searching another boundary line existing therebetween within a narrow range interposed between the extracted boundary lines, thereby reducing the extraction time.